I have enough 6AN8A tubes to run my Dynaco Mk II amplifiers well past my lifetime, but if I recondition some of the ones sleeping on shelves in the garage, I may want to lay in a supply. If so, I've always found Antique Electronic easy to deal with and fast to ship.

The 6AN8A was a popular tube found in television sets but as it's not widely used in audio, it has not been produced by tube makers in Russia, China or the Slavic countries; so what you'll get is new old stock, probably USA production.

You should bookmark this excellent and easy-to-use resource, for reference when you have a question about tube types:

http://www.duncanamps.com/tdsl/tubesearch.php

You can enter the number of just about any tube and get the ratings and application data. Using this resource, 6AN8 and 6AN8A are shown as being functionally identical. Usually when a suffix is added or upgraded it represents an change in the tube, which remains back-compatible with the older type. The improvement may be functional, such as higher maximum voltage rating; or it may reflect changes in the design for better durability, resistance to vibration, or other physical characteristics (such as a glass bulb replacing a metal case in 6L6 vs. 6L6G).

This site also includes crossreference data to other tube types as a guide for substitution, including which types are identical or nearly so, which are similar but with differences in ratings or performance, which are similar but with different pinouts, and which are similar but run on different filament voltages.

For greater in-depth research, any of the several tube manuals contain even more information.

typically the A after a tube type denotes it uses a slow start filament rather than the original filament type that "flashed" brightly upon power-up due to current surge thru the nearly dead short circuit."A" type tubes were made so that tubes could be wired in series to share an equal amount of current properly.Most tubes have been type "A" since the mid-60s.Another common suffix is "W" and is usually WA or WB, denoting a heavy duty version of the updated tube.